Tllh Sl'KCTUA OF STAKS AND NKIU'I,.K. 



Iff) 



Further investigations in many directions are still needed to 

 complete the story, but all the modern work tends to strengthen 

 our belief in the chemical unity of the universe, and in an 

 evolutionary development of stars from the primitive condition 

 represented by nebulae. 



Discussion. 



The CHAIRMAN (Sir Frank W. Dyson, Astronomer Royal) 

 regretted that he had not been present at the opening of the 

 Meeting, as he had been delayed by an accident on the railway 

 line. It would have given him great pleasure to have introduced 

 Professor Fowler to the Meeting. A large part of the recent 

 progress in the application of the spectroscope to astronomy had 

 been due to Professor Fowler's own work ; he it was who had been 

 successful in identifying the dark bands in the orange stars, with 

 bauds given by the oxide of titanium ; similarly he had identified 

 the elements giving rise to the dark bands seen in the spectra of 

 sun-spots ; he had obtained photographs of the spectra of the tails 

 of comets, and identified the corresponding elements ; he had also 

 identified some of the most interesting hydrogen lines in stellar 

 spectra. In many ways the Lecturer had made contributions to 

 science in this department of the very greatest importance. 



The subject of stellar spectra is one of great complexity, for 

 the stars present us with differences, not only in the substances 

 shown, but in the temperatures at which they exist, and these 

 may be so high that we are not able to work with them in our 

 laboratories. The result of between 50 and 60 years' work has 

 been to show how the spectra of stars may be classified, and that 

 they can be arranged in a continuous sequence. In chemical con- 

 stitution they are very like the sun, and they differ from it in that 

 some are hotter and some are cooler, the temperatures ranging 

 from about 3000 degrees C. up to 12,000 degrees C. When we 

 notice that these two lines of observation agree — that is to say that 

 we get the same order of sequence when we group the stars 

 according to their temperatures as when we group the stars 

 according to their spectra, we must conclude that we are watching 

 stars that are in the process of cooling. It is difficult to take any 



